Refrigeration system embodying aircooled condensers



Dec. 19, 1961 w, 1. GRANT ET AL 3,013,403

REFRIGERATION SYSTEM EMBODYING AIR-COOLED CONDENSERS i Filed May 22,1959 2 Sheets-Sheet 1 INVENTORS W I. Gen N E. J. Koch' e BY Wmwwzw Dec.19, 1961 w. GRANT ET AL 3,013,403

REFRIGERATION SYSTEM EMBODYING AIR-COOLED CONDENSERS Filed May 22, 19592 Sheets-Sheet 2 INVENTORS' W I. Gen/v7- E. J. KocA-nsz BY [and consinFiled May 22, 1959, Ser. No. 815,039 6 Claims. (Cl. 62-475) Thisinvention relates generally to improvements in the art of refrigeration,and it relates more specifically to improvements in the construction andoperation of compound compression refrigerating systems preferablyembodying air-cooled condensers operable by air derived from the ambientatmosphere.

The primary object of the present invention is to provide an improvedrefrigerating system comprising several stages each having a compressorand a cooperating condenser, and which are automatically cooperable witha common receiver for supplying refrigerant to the evaporators so as tomaintain a predetermined receiver discharge pressure.

Because of the shortage and resultant high cost of water in variouslocalities it has heretofore been customary to utilize condenser unitsfor the volatile refrigerant being which function independently ofatmospheric conditions have heretofore been utilized. While thesespecial devices which are necessarily relatively sensitive, complicatedand costly appear to perform their intended function, they utterly failto take advantage of low temperatures prevailing the ambient atmosphereduring certain seasons of the year. i

A system which is in fact capable of automatically taking full advantageof such low air temperatures will obviously operate at considerablylower cost than is possible with these prior installations embodyingair-cooled condensers, and may also operate more economically thanrefrigeration systems utilizing water-cooled condensers. This isespecially true is vicinities such as the northern portions of theMid-West and Eastern areas of the United States, where in spite of thefact that relatively cool water is constantly available from the GreatLakes the winter air temperatures are still far below that of the lakewater. For example, the average mean temperature in the vicinity ofMilwaukee throughout the year is only 46.8 F. which is considerablybelow the average lake and well water temperatures, so that anyrefrigeration installation embodying air-cooled condensers and which iscapable of taking advantage of low seasonable temperatures will functionmost economically.

It is therefore an important object of this invention to provide asimple and automatically functioning refrigerating system utilizingair-cooled condensers, and which takes full advantage of variations inout of doors temperatures. I

Another important object of the present invention is to provide animproved refrigeration installation having two stages each comprising acompressor and an air-cooled condenser, both cooperating with a commonreceiver for delivering refrigerant to one or more evaporators, and

wherein one stage alone is operable when ambient air temperatures arelow but both stages function when said temperatures rise.

A further important object of the invention is to provide a compoundcompression refrigerating system embodying several condensers operableby atmospheric air, and wherein the initial condenser is capable ofcompletely condensing all of the refrigerant being circulated throughthe system during cold weather periods, but is automatically assisted inthus condensing said refrigerant whenever warmer Weather conditionsprevent the initial condenser from effecting such complete condensation.

Still another important object of this invention is to provide animproved refrigeration installation involving relatively low and highpressure compression stages each including a condenser operable byatmospheric air, and in which the initial low pressure stage functionsalone to maintain proper pressures in the receiver which supplies thecooling coils with volatile refrigerant during cold Weather, while thesubsequent higher pressure stage functions only when the initial stagefails to properly maintain such receiver pressures due to increases inatmospheric temperatures.

An additional object of the invention is to provide an improvedrefrigerating system embodying air-cooled condensers, which is easy toinstall and to maintain, and which functions automatically andeconomically by taking maximum advantage of cold weather temperatures.

These and other more specific objects and advantages of the inventionwill be apparent from the following description.

A clear conception of the features constituting the present improvementand of the construction and operation of a typical commercialrefrigeration installation embodying the invention, may be had byreferring to the drawings accompanying and forming a part of thisspecification wherein like reference characters designate the same orsimilar parts in the various views.

FIG. 1 is a diagram illustrating a commercial installation embodying ourimproved compound compression refrigerating system operable withair-cooled condensers;

FIG. 2 is a central longitudinal vertical section through theintercooler and receiver unit constituting part of the system showndiagrammatically in FIG. 1; and

FIG. 3 is a similar section through the special float actuated valveinstalled in the second compression stage of the same refrigerationsystem.

While the invention has been shown and described herein as having beenembodied in a two-stage compression refrigerating system operable byair-cooled condensers to cool an insulated storage space, itis notintended to confine its application to such systems; and it is alsocontemplated that specific descriptive terms employed herein be giventhe broadest possible interpretation consistent with the disclosure.

' Referring to the drawings, the two-stage compression system showntherein is especially adapted to take full advantage of out-doortemperatures, and comprises'in general an evaporator or cooling coil 5;a receiver 6; a main compressor 7 cooperable with an initial air-cooledcondenser 8 constituting an initial stage adapted to compress andcondense all of the refrigerant gas delivered from the evaporator 5 tothe receiver at the proper pressure when the ambient atmospherictemperature is sufficiently low; and an auxiliary compressor 9.cooperable with a second air-cooled condenser 10 and constituting asecondary stage adapted to automatically further compress and condenseany excess gaseous refrigerant which the initial stagehas failed toliquefy whenever the ambient atmospheric temperature has risen.

' The'cooling coil 5 is located within an insulated chamber or cooler 12and is provided in its liquid refrigerant supply line 13 with athermostatic expansion valve 14 and in its air inlet with an electricmotor driven blower 15 for circulating the cold air around the coil; andthe upper gaseous refrigerant outlet of this coil is connected to thesuction line 16 of the main electrically driven compressor 7. Thedischarge line 17 of this compressor is provided with a non-return checkvalve 18 and communicates with the inlet of the initial air-cooledcondenser 8 preferably located in the ambient atmosphere as upon theroof 19 of the building in which the cooler 12 is confined. Theair-cooled condenser 8 is provided with an electric motor driven fan 20for drawing ambient air over its heat transfer surfaces and around itspropelling motor, and the discharge line 21 of the condenser 8 isadapted to deliver refrigerant by gravity into the bottom of thereceiver 6 through a perforated distributing tube 22 extendingthroughout the length of the receiver shell, as shown in FIG. 2.

The receiver 6 which normally functions merely to confine an abundantsupply of liquid refrigerant at a predetermined pressure also functionsas an inter-cooler during certain periods as will be later explained, isadapted to deliver liquid refrigerant through an outlet pipe 24 at itsbottom and past a valve 25 into the line 13 leading to the evaporator 5,and the line 13 is also provided with a charging and drainage valve 26which is normally closed, see FIGS. 1 and 2. The receiver 6 is alsoprovided with a liquid level indicating gauge 27, and is additionallyprovided with an outlet pipe line 28 for gaseous refrigerant at the topof its end remote from the condenser discharge line 21 and with a liquidrefrigerant return pipe line 29 intermediate its ends, but these twopipe lines 28, 29 are active only when the initial air-cooled condenser8 fails to completely condense the gaseous refrigerant passingtherethrough.

The gaseous refrigerant outlet line 23 constitutes the suction line ofthe auxiliary compressor 9 which is also electrically driven and adaptedto deliver refrigerant at considerably higher pressure than prevails inthe receiver 6, through its discharge line 31 and past a non-returncheck valve 32 into the secondary condenser 10. This condenser is alsopreferably located in the ambient atmosphere on the building roof 19 andis likewise provided with an electric motor driven fan 33 for drawingatmospheric air over its heat transfer surfaces and around its drivingmotor, and the discharge line 34 of the condenser 10 is connected to theupper portion of the casing 35 of a special float valve assemblagehaving a liquid refrigerant discharge pipe 36 communicating past asolenoid actuated valve 37 with the refrigerant return line 29 of thereceiver 6, see FIG. 3. Located within the casing 35 is a needle valve38 operable by a float 39 which rides upon liquid refrigerant confinedwithin the casing but shuts off communication with the receiver 6 whenthe second compression stage is idle. The receiver 6 is also providedwith a pressure actuated switch 46 which is automatically operable tostart the compressor 9 and the condenser fan 33 and to open the valve 37so as to cause the second stage to function under certain conditions tobe later explained.

When the improved refrigeration system has been constructed andinstalled as hereinabove described, its operation is substantially asfollows: Whenever the outside temperature is low and it is desired tocool the chamber 12, it is only necessary to operate blower and the fanand the main compressor 7 thereby causing the latter to withdraw lowpressure refrigerant gas from the evaporator 5 through the suction line16 and to compress and deliver the gaseous refrigerant to the initialair-cooled condenser 8 through the discharge line 17. The fan 20 of thiscondenser will then circulate the cold atmospheric air' around the heattransfer surfaces to condense the refrigerant and the resultant liquidrefrigerant will gravitate through the line 21 and will enter thereceiver 6 through the perforations in the tube 22 which is immersed inan abundant supply of liquid refrigerant initially admitted to thereceiver past the valve 26. The pressure within the receiver 6 may bemaintained at a predetermined desired value by proper operation of themain compressor 7, and the expansion valve 14 will then function tometer the liquid refrigerant delivered under pressure from the receiver6 to the evaporator 5 through the line 13, thus causing the initialstage alone to function as a complete refrigeration system as long asthe ambient air temperature is sufficiently low to effect substantiallycomplete condensation of all refrigerant being circulated through theevaporator.

During such operation of the system, the auxiliary compressor 9 and thesecondary condenser 10 will remain idle, but if the outside airtemperature rises sufficiently so that the initial condenser 8 isincapable of condensing all of the gaseous refrigerant delivered theretoby the main compressor '7, then the uncondensed refrigerant gasdelivered into the receiver 6 through the perforations in the pipe 22will bubble up through the liquid refrigerant in the receiver 6 in amanner similar to the action which takes place in an intercooler. Therefrigerant gas thus admitted to the receiver 6 accumulates above theliquid and promptly increases the receiver pressure sufficiently toactuate the pressure switch 40 and to thereby start the auxiliarycompressor 9 and the fan 33 and to open the solenoid valve 37, whereuponthe compressor 9 withdraws the refrigerant vapor through its suctionline 28 and further compresses the excess gaseous refrigerant while alsoincreasing its temperature sufficiently to enable the secondarycondenser 10 which receives the compressed gas through the compressordischarge line 31, to condense this high temperature gas even when theambient air temperature is at its highest value. The condensate from thesecondary condenser 10 gravitates through the line 34 past the floatvalve 35 and through the pipe line 29 into the receiver 6, and theinstallation thus functions as a two-stage compression system exceptthat the liquid refrigerant fed to the evaporator 5 is at anintermediate pressure.

From the foregoing detailed description of the functioning of theimproved system, it will be apparent that the present invention in factprovides a simple and effective refrigeration installation preferablyembodying air-cooled condensers and which automatically converts from asingle stage compression system into a two-stage compression system, andvice versa, dependent only upon changes in atmospheric air conditions.It differs from the ordinary two-stage compression system wherein bothstages are constantly active, and is primarily adapted for use inlocations where the cost of water for actuating the condensers is highor the use of such Water is restricted, and where the average out-doortemperature is low.

The present improved system has the advantages of simplicity and lowcost of installation and maintenance, and it also eliminates thenecessity of providing complicated water supply and sewer connections.It also functions automatically with minimum attention after beinginitially properly installed and adjusted, and the improved receiver 6operates merely as an accumulator or liquid refrigerant storage drumduring normal operation under low temperature atmospheric conditions,and as an intercooler Whenever the ambient air temperature rises and thesecond stage becomes active.

It should be understood that it is not desired to limit this inventionto the exact details of construction and operation of the compoundcompression refrigeration system embodying air-cooled condensers, hereinspecifically shown and described, since various modifications within thescope of the appended claims may occur to persons skilled in the art.

We claim:

1. In a refrigeration system, an evaporator, a main compressor forwithdrawing low pressure gaseous refrigerant from said evaporator, aninitial condenser for receiving compressed gaseous refrigerant from saidcompressor, a receiver for refrigerant delivered from said condenser, anauxiliary compressor operable to withdraw from said receiver onlygaseous refrigerant which said initial condenser fails to condense,operation of the auxiliary compressor being responsive to receiverpressure, a secondary condenser for receiving compressed gaseousrefrigerant from said auxiliary compressor and for returning saidrefrigerant in condensed condition to said receiver, and means fordelivering liquid refrigerant from said receiver to said evaporator,said auxiliary compressor and said secondary condenser being operableonly when gaseous refrigerant is available in said receiver to condensesuch refrigerant and to return the condensate directly to the receiver.

2. In a refrigeration system, an evaporator, a main compressor forwithdrawing low pressure gaseous refrigerant from said evaporator, aninitial atmospherical- 1y air cooled condenser for receiving compressedgaseous refrigerant from said compressor, a receiver for refrigerantdelivered from said condenser, an auxiliary compressor operable towithdraw from said receiver only gaseous refrigerant which said initialcondenser fails to condense, operation of the auxiliary compressor beingresponsive to receiver pressure, a secondary atmospherically air cooledcondenser for receiving compressed gaseous refrigerant from saidauxiliary compressor and for returning said refrigerant in condensedcondition to said receiver, and means for delivering liquid refrigerantfrom said receiver to said evaporator, said auxiliary compressor andsaid secondary condenser being operable only when gaseous refrigerant isavailable in said receiver to condense such refrigerant and to returnthe condensate directly to the receiver.

3. In a refrigeration system, an evaporator, a relatively low pressurecompressor for withdrawing spent gaseous refrigerant from saidevaporator, an initial condenser for receiving compressed gaseousrefrigerant from said compressor, a receiver for refrigerant deliveredfrom said condenser, a higher pressure compressor operable in responseto receiver pressure to withdraw from said receiver only gaseousrefrigerant which said initial condenser fails to condense, a secondarycondenser for receiving compressed gaseous refrigerant from said higherpressure compressor and for returning said refrigerant in condensedcondition to said receiver, and means for delivering liquid refrigerantfrom said receiver to said evaporator, said higher pressure compressorand said secondary condenser being operable only when gaseousrefrigerant is available in said receiver to condense such refrigerantand to return the condensate directly to the receiver.

4. In a refrigeration system, an evaporator, a relatively low pressurecompressor for withdrawing spent gaseous refrigerant from saidevaporator, an initial atmospherically air-cooled condenser forreceiving compressed gaseous refrigerant from said compressor, areceiver for refrigerant delivered from said condenser, a higher pressure compressor operable in response to receiver pressure to withdrawfrom said receiver only gaseous refrigerant which said condenser failsto condense, a secondary atmospherically air-cooled condenser forreceiving compressed gaseous refrigerant from said higher pressurecompressor and for returning said refrigerant to said receiver, andmeans for delivering liquid refrigerant from said receiver to saidevaporator, said higher pressure compressor and said secondary condenserbeing operable only when gaseous refrigerant is available in saidreceiver to condense such refrigerant and to return the condensatedirectly to the receiver.

5. In a refrigeration system, an evaporator, a receiver, main andauxiliary independently operable refrigerant compressors eachcommunicating with an independent air-cooled condenser both of whichcommunicate with said receiver, means for conducting spent gaseousrefrigerant from said evaporator into said main compressor, means forconducting from said receiver into said auxiliary compressor gaseousrefrigerant which the communicating condenser of said main compressorfails to condense, and means for delivering liquid refrigerant from saidreceiver to said evaporator, said auxiliary compressor being operable inresponse to receiver pressure only when gaseous refrigerant is availablein said receiver to condense such refrigerant and to return thecondensate directly to the receiver.

6. In a refrigeration system, an evaporator, an intercooler receiver,rnain and auxiliary refrigerant compressors each communicating with anindependent atmospherically air-cooled condenser both of whichcommunicate with said receiver, operation of said auxiliary compressorbeing responsive to receiver pressure, a conduit for conducting lowpressure gaseous refrigerant from said evaporator into said maincompressor, a conduit for conducting from said receiver into saidauxiliary compressor gaseous refrigerant which the communicatingcondenser of said main compressor head fails to condense, means fordelivering liquid refrigerant from said receiver to said evaporator, andmeans for effecting actuation of said auxiliary compressor only whengaseous refrigerant is available in said receiver to condense suchrefrigerant and to return the condensate directly to the receiver.

References Iited in the file of this patent UNITED STATES PATENTS

